docs: def _vertical_segment(old_offs, new_offs, spacing, radii):
      '''Vertices for a vertical rectangle
      '''
      return np.array(((new_offs[0] - radii[0], old_offs[1] + spacing[1]),
                       (new_offs[0] - radii[1], new_offs[1]),
                       (new_offs[0] + radii[1], new_offs[1]),
                       (new_offs[0] + radii[0], old_offs[1] + spacing[1])))